topic DEM data resolution in Data Management Questions

DEM data resolution

TopMap — Tue, 11 Dec 2012 16:05:19 GMT

The client supplied me with the DEM but did not specify what resolution this data is. Can someone tell me how to check the resolution of the DEM data. I need this data to have resolution of 30m but not sure how to verify it. Does it make a difference if data is in WGS_84 projection?

Many thanks!

Re: DEM data resolution

JakeSkinner — Tue, 11 Dec 2012 17:56:21 GMT

Hi Lila,

Spatial Resolution refers to the cell size (the area covered on the ground and represented by a single cell). See here under 'Types of Resolution'. Therefore, if the cell size is 5 x 5 meters, the resolution is 5 meters.

You can check the cell size by right-clicking on the raster dataset > Properties > Source tab. If your coordinate system is in a Geographic WGS 84 coordinate system, you will want to project your raster to a projected coordinate system with Meters for the linear unit. You can do this using the Project Raster tool.

Re: DEM data resolution

EricRice — Tue, 11 Dec 2012 18:40:21 GMT

If the data is in GCS_WGS_1984 you will find the cell sizes in the properties to be a little confusing, as well as having quite small values. This is because the units are in decimal degrees, not meters/feet. For example, I have some 30m ASTER data for the world, but when I check the properties the cell size is 0.00027777778, which is due to the data being in GCS.

If you plan on analyzing the dem, you should project it such that the linear units are the same as the vertical units so that X, Y, and Z are consistent, otherwise expect to be calculating Z factors and using them when appropriate. Note that Z factors change with latitude so if your extent is very large a single Z factor won't cut it.

When projecting a dem, do not accept the default resampling in the Project Raster tool. Switch it to bilinear to save yourself some headaches down the road. Nearest resampling is not meant for a dem.

Best,
Eric